pg-migration

PostgreSQL schema migration safety reviewer and DDL generator. ALWAYS use when writing, reviewing, or planning PostgreSQL schema changes — ALTER TABLE, CREATE/DROP INDEX, column type changes, constraint additions, RLS policy changes, or any DDL touching production tables. Covers lock-level analysis, CREATE INDEX CONCURRENTLY, NOT VALID constraint patterns, transactional DDL rollback, pg_repack for table rewrites, phased rollout design, and backward compatibility. Use even for "simple" ADD COLUMN — PostgreSQL DDL lock behavior varies by operation and version, and AccessExclusiveLock on a hot table causes immediate outage.